TEHRAN, Iran (CNN) -- Gunmen on motorcycles fired Friday on a campaign office for President Mahmoud Ahmadinejad, wounding two adults and a child, according to a report by Iran's state-run news agency.

President Mahmoud Ahmadinejad was not present at the time of the attack.

The shooting happened about 5 p.m. in front of the entrance to the campaign office, campaign representative Mohammed Reza Zahed Shaikhi told IRNA.

Ahmadinejad, who is running for a second term in office, was not present. Iran's presidential election will take place on June 12.

The attack happened in Sistan-Balochistan province in southeastern Iran, the same province where a Shia mosque was bombed Thursday. Several suspects have been arrested in connection with Thursday's attack in the town of Zahedan, which killed between 15 and 20 people, according to Iranian media reports.

No group publicly accepted responsibility for the mosque attack, but the provincial governor, Ali-Mohammad Azad, blamed a terrorist group that he said would be unveiled to the public once the suspects have been interrogated, IRNA reported.

Zahedan is about 1,100 km (700 miles) southeast of Tehran, near Iran's borders with Pakistan and Afghanistan.

Sistan-Balochistan province -- which shares a border with Pakistan -- is the site of frequent clashes involving Iranian police, drug dealers and armed groups. The province is located on a major narcotics-smuggling route between Afghanistan and Pakistan.

Azad said information on the arrested terrorist group would be unveiled to the public once interrogations were complete.

"The terrorists and notorious gang planned to stir order and security in the province on the eve of (the June 12 presidential) elections, using ongoing insecurity in our eastern neighbors," he said Thursday.

Several days of mourning were reported to be under way for victims of the explosion.

Ayatollah Ahmad Khatami, a hard-line cleric who led Friday prayers in Tehran, said there were signs that the United States and Israel were involved in the mosque bombing, IRNA reported. The cleric, who put the death toll at 25, condemned the bombing before a congregation on the Tehran University campus.